I think, but could be wrong.
That it would take him 6-12 months to upgrade to captain, no direct entry captains.
Then, he would be seat locked for 2 years as a captain, then he would be competing through the bidding system with everyone else.
So, it just depends on when he joins and what his number on the seniority list is relative to everyone else who will also be looking to get on to a large cabin plane.
Almost an impossible question, I think only the minimum of 3 years can be said to get to the point of being able to bid, then it is down to a large set of variables. ( seniority, types available at that time for bidding, how many people bid for that type, etc, etc)